Filters generally consist of a fine mesh screen that is capable of stopping particles which are entrained in a fluid stream that is passing through the screen. The size of the particles, naturally, must be greater than the size of the mesh. To capture particles having diameters less than 100 microns, the use of such mesh screens is generally impossible in that meshes of such sizes are difficult to manufacture. Stack disc filters, therefore, are used for capturing minute particles of this size range. When particles are in the range of 5 to 25 microns, prior art stack disc filters generally employ filtering discs which have etched passageways, undulating surfaces or roughened surfaces. This dimensional range is also known as the sub-mil range since one mil, one-thousandth of an inch, is approximately 25 microns. Examples of filters employing such filtering discs include Hagler, Jr., U.S. Pat. Nos. 4,410,430; Pearson, 3,648,843; and Toth et al., 3,397,794. These filters, however, contain several deficiencies one of which being the added expense of manufacturing the passageways, the undulations and the roughened surfaces. Another deficiency is the necessity of using higher pressures to propel fluid through these filtering discs. Moreover, such filters are difficult to clean. In any event, none of the prior art filters is capable of filtering particles which are less than one micron in diameter.